There are known many vessels incorporating suspension systems to resiliently and/or adjustably support a chassis portion, at least partially, relative to one or more hulls. The Applicant's United States patent application publication numbers US2013/0233225 and US2013/0233226 show various arrangements of interconnected suspension systems for multi-hulled vessels and United States patent application publication number US2013/0213288 describes an alternative type of control actuator. The Applicant's international patent application publication number WO2013/181699 discloses a suspension geometry primarily suited to catamarans and WO2014/153600 discloses stabilisation of the chassis portion utilising gyroscopic stabilisers.
None of these advanced vessels providing suspension of the chassis portion are yet in operation on commercial offshore wind farms for example where currently conventional closed-tunnel rigid catamarans are most often used for ferrying personnel and parts to the pylon or foundation supporting each wind turbine. When the vessel reaches a pylon, the vessel is docked with the pylon by pushing the bow of the vessel into the side of the pylon to help generate sufficient friction between the vessel and the pylon to reduce relative motion. The personnel then have to judge when little relative motion is likely and transfer between the vessel and pylon as quickly as possible. This transfer activity increases in risk as the sea state increases.
It has been proposed to use multi-hulled vessels with resiliently suspended chassis portions to improve the safety of these transfers. The greater the improvement in steady state performance of a vessel docked with a pylon, the greater the safety margin, the higher the number of days servicing operations can be carried out and/or the smaller the service vessel may be thereby improving the safety and efficiency of the offshore wind farm.
It would therefore be desirable to provide a control system for a vessel incorporating a suspended chassis, the control system minimising relative motion between the pylon and at least a portion of the chassis.